Dynamic Analysis Of Composite UAV

During the flying process of UAV(unmanned aerial vehicle), there would bevibrations and noises on the fuselage because of the random oscillations of theengine and the wind. It would decrease the working precision, increase the abrasionbetween the structures, and even generate structure failure for the resonant.Especially for the inertial navigation system of the UAV. It needs high precision, itsoutput information determines the navigation accuracy of the UAV directly. So it isimportant to control its vibration sources and noise sources.The dynamic characteristics of the UAV must be investigated to solve theproblem of vibration. The main tasks of this topic are as follows, countering acomposite UAV based on the theories of modal analysis and mechanical vibration:（1） Built a three-dimensional demi-body model in the UG software by aseries of simplification on the basis of existing composite UAV. Exported the modelto the fea software Patran, created the fea modal model of the composite UAV.There were304973finite element meshes and400785nodes created in the wholemodel.（2） Linearized the model without considering the structure damping.Developped theoretical modal analysis of the UAV fea model with the solverNastran, getting the first50free-modal information of the UAV. Applied theimputed motor dynamic load on the UAV model and obtained its responses.（3） Experimented the modal of the composite UAV and the responses ofthe fuselage under the motor excitation, getting the modal information of the UAV which was interested. Compared the results with the theoritical analysis andcorrected the model. And obtained the vibration information of the inertialnavigation system under motor excitation which would guide the design of thevibration isolation of the inertial navigation system.（4） Designed the vibration isolation of the inertial navigation system.Simulated the vibration of the inertial navigation system under the random roadroughness during the taxing and landing processes of the UAV. An optimizationmodel was set up in which the elastic coefficient k and damping coefficient c wasregarded as optimization variable. The simulation results showed that when k was3700N/m and c was0.455N·s/m, the root mean square of acceleration of inertialnavigation system decreased as45.1%lower than the before one, decreased thevibration of the inertial navigation system under the random road roughness greatly.This topic obtained the modal information of the composite UAV throughsimulation and experiment, getting an engineering-realizable rubber structure forvibration isolation. It can provide advice for the design of vibration isolation foraerospace inertial navigation system.